Kokoro
by VongolaXII
Summary: A robot was built by a lonely scientist, To say how it was done, miracle But something was missing, there was one thing he couldn't do and that was the program called 'a heart'. Inspired by Kagamine's song. AU R27 and many pairings more. Slow development, rating will change depending on the progression.
1. Chapter 1

**Disclaimer: I don't own anything**

**Claim: I own the story**

* * *

**A/N: …I'm aware that I am starting a new story but I couldn't help it! ;-; Also, forgive me for removing stories. I found them really annoying so yeah. I'm so sorry. And I admit I got this idea from Kagamine Rin's "Kokoro" song. :') It's really sad.**

* * *

**.**

'_A robot was built by a lonely scientist,__  
__To say how it was done, miracle__  
__But something was missing, there was one thing he couldn't do,__  
__and that was the program called a __**heart**__'_

**.**

* * *

The room was dim, because light only passed through the thin hole created by the cracks on the hole. A clock hung on the wall, ticking on. It showed eleven forty-five in the morning. The man smiled as he worked on. His brown hair turned gold whenever he moved and the rays hit them. His hand never stopped connecting the wires.

Tsunayoshi Sawada, or formerly known as Dr. Tsuna, was busy stuffing wires into appropriate hole of the figure. He was in his own mini lab, just under his study room. He used to work with the Vongola Lab but he resigned when they critique and despised of his idea of creating a robot. They told him it was possible but takes a lot of fund.

The brunet wasn't going to let them win. He resigned and took his salaries away with him and moved away from Tokyo. He lived in a small house. At first, he was wary of the house's condition. But when he discovered the crack on the floor which leads to his current lab, he immediately bought the house. With the money left, he started on his invention. He rarely went up to his room. There was a fridge that he brought down to the lab. The toilet was also built by him at the corner of the room.

It was a perfect lab for him.

* * *

Two years have passed since he started working on the robot. His eyes turned puffy and he grew thinner. But that didn't stop his wish of getting his invention done. When the clock lets out a heavy 'tong' sound, Tsuna looked up. It showed six in the evening. He yawned. He had been staying up late for months now.

The brunet quickly connect all the wires and walked towards his controlling machine. There, he pushed a yellow button followed by the green button. Light emit from the robot's eyes and Tsuna's eyes gleamed with excitement. He continued typing on the keyboards.

The robot shook and it's eyes was filled with live. Tsuna looked satisfied. He left the machine and approached the robot. He looked up at it proudly.

_This is it, I've made it!_ He thought excitely.

He touched the robot's skin. It felt soft and natural. "Hello, I am your creator, Tsunayoshi Sawada," he smiled at the robot. The robot, given the name 'Reborn', merely stared at his creator. He did not speak but his eyes bore into Tsuna's eyes. Tsuna beamed. "Your name is Re-born."

"...Re...born." the robot's voice came out electrical. Tsuna nodded. He repeated the word. "My name...is Reborn."

Reborn had black spiky hair with a tall, fit body. From faraway, one might view him as a hot human but if they look closer, lines could be seen under his chin. Tsuna created Reborn to fill in his lonely life; he had no family, no spouses and no friends.

He was alone.

"Yes, you are Reborn. From now on, you are my friend." Tsuna smiled. He held out his hand towards Reborn. The robot tilted his head slightly. Tsuna urged him to shake it. They shook hand. Tsuna was beyond pleased at his succession.

* * *

The next day, the brunet left Reborn alone at home and went out shopping. After two and a half years, he finally get to breath fresh outside air. All these times he was locked in his lab, not knowing what had happened to the outside world. Tsuna visited a casual shop, buying Reborn a few shirts, jeans and scarfs. Then he walked around the town, looking for something to eat.

"T-Tsuna?" he turned when he heard someone addressing him so familiarly.

A silver haired man stood there, with an ice cream half in his mouth. His green eyes stared at Tsuna, making the brunet awkward.

"Um, do I know you?" Tsuna asked.

"I'm Gokudera Hayato, your assistant two years ago," the silverette answered. "You're getting thinner...how's life?"

Tsuna smiled at the ground. "I'm fine." he muttered.

Gokudera bit his lips. He was finding for something to say. "U-Um, about your plan that year, have you...achieved it?"

"Huh?"

"You know, the...robot plan." Gokudera scratched his cheek slowly. He hesitated if he should bring up the topic. He felt bad for not supporting Tsuna when the brunet revealed his plan. He didn't know if Tsuna could actually do it or not so he didn't say anything to back up his leader. The guilt was with him even after two and a half year.

A smiled crept on Tsuna's face. "Well, it's going fine." he said, smiling. Then he checked his watch. "Ah, I got to go. Reborn is waiting for me. See you, Gokudera!" Then he rushed away.

The silverette stared as Tsuna ran away. Reborn? Why does that name sound so...familiar?

* * *

"I'm home—"

Reborn looked up from his actions. The plastic bags that Tsuna was holding fell on the floor, the contents falling out. His jaw hanged open, shocked. The robot stood up. "Tsuna." was his short reply.

The brunet looked around. "Y-You cleaned this?" he asked in disbelief.

Reborn nodded. "I saw that it was dirty. Dirty things must be cleaned." he answered. Tsuna nodded.

"That's very nice of you..." he praised. Reborn's eyes gleamed in happiness. He hugged his creator suddenly. Tsuna yelped, surprised. Although Reborn was a robot, but he could feel his body heat. How is this possible?

Confused, Tsuna hugged back.


	2. Chapter 2

**Disclaimer: I don't own the characters**

**Claim: I own the story**

* * *

**A/N: I don't want to promise anything because I can't do it, usually…I'm having my mid-term exams now and it's really, really important for my grades. But I will still write on Saturdays…just when I update, I don't know. :)) Thanks for the support! I forgot to say that they are all in adult form here.**

* * *

_. _

'_The tiniest bit of guilt is what makes you today, I did not ask you to stay; maybe one day I'll win back you, or I'll lose you.'_

_._

* * *

He rubbed his temple, mind racing. He swore that the name was very familiar; he had heard it somewhere. He pressured his memory gland to work, trying to remember where he'd encounter that name. Then, something clicked.

"_I'm going to build a human android!" _

"_No one will pull me down, even you, Gokudera."_

"_I'll name him Reborn. He will be my very first best friend."_

Reborn.

Gokudera's eyes widened. _Don't tell me he—_the silverette looked shocked.

"_I got to go now, Reborn is waiting for me!"_

No wonder it sounded so familiar. It was the name of Tsuna's plan, his very first creation. Gokudera couldn't help but feel amazed at Tsuna's achievement. The brunet was still going after that dream even though he had no supporters behind him.

But he couldn't help feeling a tiny spark of jealousy in his heart. Before Reborn was created, he was Tsuna's best friend. He was his assistant. He followed him everywhere to research. He was with him. But ever since the incident of Tsuna resigning, Gokudera feel a large, thick wall had built between them. They rarely meet, not to mention talk—even through the phone.

It was not like Gokudera had not tried to contact the brunet. Tsuna changed his number. He disappeared. And then just now, Gokudera spotted him on the town.

Where did he live?

* * *

Tsuna placed the plastic bags on the counter. He called out for Reborn. The house was clean, like a brand new house. A few seconds later, the robot appeared from the store room. His body was dusty. The brunet chuckled at Reborn's dirty self. Reborn walked towards his master, holding something. He handed it to Tsuna.

"I found this in the store room. I saw your face. Are these your friends, too?" The raven asked.

Tsuna bit his lower lips when he saw the photograph. It was a picture of him with Gokudera and the rest of his workers before he left. He felt a pinch of pain in his heart. Unconsciously, his fingers caressed the photo. Sorrow flooded his eyes as he scanned each of the faces. Then his eyes fell on that particular face.

A raven with sharp eyes stared back at him.

Reborn only stared at Tsuna who seemed to be rooted to the floor, drowned in his own thoughts. After five minutes, he walked away from Tsuna, approaching the plastic bags. He peered inside. He pulled out a black shirt with a hoodie. Reborn touched Tsuna's arm.

The brunet flinched. He was immediately pulled back to reality.

"…Yes, Reborn?" he asked slowly.

"This shirt is pretty." Reborn replied. Tsuna smiled. His memories seemed to fade away.

"It's for you, do you like it?" the brunet beamed. Reborn smiled slightly at Tsuna. He examined the shirt by turning it back and forth. Then he nodded. Tsuna looked pleased. He tilted his toes to brush off dirt from Reborn's hair. The other didn't move. He let his master to keep brushing.

* * *

During evening, Tsuna bought dinner for them as he does not know how to cook. _I'll have to start learning all these, _he thought. He glanced at Reborn who was staring at the plate of instant spaghetti.

"Aren't you eating?" he asked Reborn.

The robot stared at him blankly. Tsuna blinked. Only then he realised that Reborn wasn't a real human. But he wasn't going to give up yet. He waved his hand in front of Reborn to gain his attention. When Reborn was paying attention, he started.

He taught Reborn how to use a fork, how to twist the slippery noodles and eat it. Reborn seemed hesitated for a moment but to him, his master's order must be obeyed. He pushed the fork twisted with noodles into his mouth.

"Chew," Tsuna said eagerly. "Like this." He demonstrated it to Reborn.

Reborn followed and soon his mouth was moving. Tsuna stared at the perfect android he had created and couldn't help feeling proud. Reborn's skin was fair and smooth, his eyes well-shaped, his nose prefect and his lips…Tsuna blushed. He quickly looked down when he realize he was checking out his creation.

Then they ate in silent.

* * *

Night time came. Tsuna walked into his room for the very first time and flicked the lights on. The fluorescent light blinked before settling down. The brunet stepped in and saw that the room was in a clean state. He looked around. The room looked new.

"I thought I hadn't been up here for years…" then he whirled around and almost bump into someone. He rubbed his nose and looked up. Reborn was standing there. "Eto, y-you cleaned the room, Reborn?" he stuttered.

Reborn nodded. "I cleaned the whole house. It was dirty. Dirty things should be cleaned up," he replied.

"Oh…"

The brunet took a bath and changed into his pyjamas. He saw Reborn standing beside his bed and frowned. "Why don't you lie down?" he tilted his head slightly. There was only one room so Reborn will have to sleep with him. He climbed on the bed and patted to the space beside him. Luckily, the owner left a big bed in the room. "Here."

Reborn looked confused. He continued staring at Tsuna. The brunet sighed. "Come here, Reborn. Lie down, like this." He lied back and sighed contently. Reborn followed. Soon, he was lying down beside Tsuna. Tsuna could feel the warmth from the other's body. Safety surrounded him.

He yelped when he felt someone hugging him. Reborn wrapped his arms around Tsuna, pulling him close. Then his eyes' color dimmed. Then, he fell asleep. Tsuna could feel the thumping of his heart. He didn't know what made Reborn to like hugging a lot, but he felt safe. After a minute, he was snoring away.

* * *

"Um, excuse me, are you looking for a worker?" he asked the receptionist. The girl smiled kindly at her.

"Right this way please, sir." She gestured him towards the waiting room. "Our boss will be here shortly. Please hold on." Then she walked away.

Tsuna was nervous. He was out again, looking for jobs. He told Reborn to take care of the house when he worked. He wanted to start saving money to buy a bigger house. He was feeling rather uncomfortable living in a house with a forest behind it. Plus, electricity was limited and the water was sometimes dirty. He hadn't realized it before but now, he was more aware of it.

The door creaked open.

Ba-dump, his heart was beating abnormally. A man with spiky black hair and sharp eyes entered the room with a friendly looking man behind him. The friendly man closed the door. The taller man sat in front of Tsuna and crossed his leg. His secretary stood beside him. The brunet swallowed.

"So you're the one who applied to be my office boy?" the man spoke. Tsuna's heart shuddered slightly at his calm and cool tone. He nodded. The man cocked his head to the right and stared at Tsuna.

"Do you have any working experiences?"

"U-Um, I worked as one of the elite scientists in the Vongola Lab before…" Tsuna muttered. He was very nervous. His voice was shaking.

The man's eyes widened a little. His eyebrow arched. "Vongola Lab…Tokyo's top three lab?" he asked.

Tsuna nodded.

"…Alright, my name is Yamamoto Takeshi. I am the Chief Executive Officer, the boss here. You can call me Yamamoto-san. You're hired." The raven smiled a little. Tsuna's jaw fell.

"I-I'm hired…?" he asked in disbelief. He had just sat here not more than five minutes and he was hired? He pinched himself and yelped when pain stung him. Yamamoto chuckled.

"Yes, you are hired. I won't question further because I am sure that you are capable of working here. Oh, and Asari? Put, uh…" he glanced at Tsuna.

"Tsuna—my name is Tsunayoshi Sawada," the brunet quickly answered.

Yamamoto smiled. "Put Sawada under the Research Section, I remember there's an empty slot there. Irisawa left last week, right?" Tsuna gaped. He was just applying for an office boy job…but he got a higher post instead? He couldn't believe his luck.

The man named Asari nodded. He bowed at Yamamoto then looked at Tsuna. "Hi, my name is Asari Ugetsu. You can call me Asari as I don't like formalities. I am Yamamoto-san's secretary." He introduced himself.

"N-Nice to meet you too…"

Asari smiled. "Well, let's get to work. I'll tour Tsuna then, Yamamoto-san. Don't forget your meeting with G-san today, three o'clock sharp." He said, reading out Yamamoto's schedule. The raven scrunched his nose. He waved a hand at Asari.

"Please, I know it. You're repeating it for the tenth time." He moaned. Asari grinned. Then he motioned Tsuna to follow him to walk around the building.

* * *

"G, your meeting is going to be at three. Its two twenty now." Gokudera informed his boss. The red hair glanced at the clock on the ceiling. Then he looked at Gokudera.

"Get my coat and bag ready," he ordered. "I'll be downstairs in five minutes."

Gokudera nodded and walked out of the room. After Tsuna resigned, Gokudera left two months later. He then worked with his cousin, G, in his research company. At first he was reluctant but since G agreed to pay him and offered him the secretary place, he joined the Storm Research Foundation.

* * *

The meeting was held in Yamamoto's company's meeting room. G arrived with Gokudera. Yamamoto and Asari were already in there. They shook hands and G sat down. His secretary stood beside him. The same goes to Yamamoto's secretary.

Yamamoto's meeting room was not very spacious like his office because he rarely held meeting in his company. Usually it would be in the other party's company or outside. But for G, it was a special case since their companies were 'quite' close.

"Good day, G-san," Yamamoto smiled. G merely stared at Yamamoto. He wasn't very fond of socializing. He was the boss only because he was fulfilling his father's will. But his abilities shone when he took over the company. He was fitted to be the boss.

"To you too," was his short reply.

Yamamoto was still smiling. It wasn't rare for G to not to smile. He had seen it many times. He took a file from Asari. "Well, I heard that you're offering to cooperate with my company to research a special item for his Highness?" he started, flipping through the file.

The Storm Research Foundation and Yamamoto Private was the top research company after the Vongola Lab. Both of them worked for the royal families and they had been asked to research an item to lengthen the King's life. At first, G was going to reject this project because according to him, the length of one life depends on God. But when he knew that Yamamoto was accepting it, he felt challenged. He never liked to lose.

G's face was still neutral. "Yes. I don't really want this project. I have requested to cooperate with you. His Highness said yes, as long as the item is created." He explained.

"Don't you think his Highness was being a little ridiculous?" the raven chuckled and rubbed the back of his neck. G did not answer. Gokudera rolled his eyes at Yamamoto. Asari coughed to ease the awkwardness. Yamamoto blinked.

"Uh, well. Alright, I agree to cooperate with you. But you do know that half of the fund should be—"

"Paid by _me, _right? Yes, I got it. I'll pay." G cut in. Yamamoto smiled. "Is that all? Then I'll leave." G was standing up.

"Wait! I have to get the name of your researchers. I need to list down their names in my report." Yamamoto said.

G clicked his tongue. Impatient was plastered on his face. "Gokudera, the list." The silverette passed a piece of paper to G. G scanned the paper in two seconds and handed it to Yamamoto. Asari took the paper. G glared at the man. Asari pretended he saw nothing.

"Hayato Gokudera, Ryohei Sasagawa, Bianchi Gokudera and Basil, correct?" Yamamoto read out. G nodded. He looked impatient. Yamamoto handed a piece of paper to G. G snatched the paper rudely. He read it.

"Asari Ugetsu, Lal Mirch, Colonnello and Tsunayoshi Sawada." He read. Yamamoto nodded.

Gokudera's eyes widened. Was the name just a coincidence or…his heart began jumping abnormally. Tsunayoshi Sawada? Since when…? Thousands of questions swarmed through his mind at the moment. He was sure that it wasn't a coincidence. It was Tsuna.

And since the researchers will cooperate together, it means that Gokudera will be working together with Tsuna. Once again, they will be working under the same lab, but with a different relationship now.

* * *

**A/N: .3. I don't know anymore. Eh, Yamamoto suddenly popped out from nowhere.  
**


End file.
